The present invention relates to an electrical current transfer assembly, and particularly to the type including a slip ring and a brush ring (sometimes called a wiper ring) having an annular array of contact elements (sometimes called wiper elements) engaging the slip ring as one ring, usually the slip ring, rotates with respect to the other ring.
Such assemblies are commonly used for transferring electrical current between a fixed part and a rotary part of an electrical device or transmission system. In the known arrangements, it is common to have the contact elements uniformly vary in length so as to engage different surfaces of the slip ring and thereby to distribute the wear on the slip ring. Examples of such known construction are illustrated in U.S. Pat. No. 2,937,224 and British Pat. No. 1,216,886. These known arrangements, however, tend to produce unbalancing forces on the slip ring since the contact elements engaging the slip ring at a greater radial distance from its center of rotation produce a greater element of force thereon than the contact elements engaging the slip ring at a smaller distance from its center of rotation. Such unbalancing forces affect the smoothness of operation of the assembly. In addition, they increase the rate of wear and therefore may necessitate more frequent maintenance, repair, and replacement of parts of the assembly. Further, such unbalancing forces may be particularly troublesome in arrangements including brush rings engaging the opposite faces of a slip ring coupled to rotate with a shaft, especially when it is desired to permit the slip ring to move (float) axially with respect to the shaft.